Sparking plug



April 5, 1938. oss 2,113,516

SPARKING PLUG Filed June 16, 1937 ve v an Patented Apr. 5, 1938 PATENT OFFICE SPARKING PLUG Aurelio Possenti, Rome, Italy Application June 16, 1937, Serial No. 148,606

I In Italy July 16. 1936 2 Claims.

In explosion engines, especially those in which the compression ratios are of high value, the sparking plugs are subjected to very high temperatures so that the central electrode of the sparking plug is very severely strained.

It is well known that this electrode is very much hotter than that of the mass, and therefore, in order to prevent its wean-which depends from many factors, such as material used, shape'of electrode, temperature of its tip, intensity of current, and so forth,-it is necessary to find means for automatically controlling the heat of the central electrode so that the ratio between the quantity of heat absorbed by the plug and that yielded to the exterior is reduced to a minimum compatible with the maximum temperature, and that the said ratio is possibly constant.

The object of the present invention is to obtain a sparking plug with nearly constant temperature which is also adapted for any type of engine so that the heat of the central electrode will be partly given off'to the exterior before, the subsequent ignition takes place.

This object is realized by means of a simple metal body (sodium) in liquid condition, or a fusible metal alloy always in liquid condition and continuous circulation with a speed variable according to the temperature reached by the terminal of the central electrode.

In this way there occur automatically modifications in the body of the central electrode under the point of view of the treatment of the portion of heat to be disposed of at a given time.

The transfer of this heat from the central electrode to the exterior is effected by contact, by means of a cone of electrolytic copper, compressed or strongly wrought, or also by means of some other high heat conducting metal such as silver, the said cone being kept adhering to the body of the central electrode properly insulated at the hottest points by any proper means.

The annexed drawing shows by way of an illustrated example a form of sparking plug of nearly constant temperature, entirely diflerent from any other type of sparking plug hitherto used, called hot and cold, or from other sparking plugs with internally bored electrode to be filled with a low melting metal or fusible eutectic salts the liquid of which, however, is not in continuous circulation in the interior of the central electrode.-

.Into theintemally bored. electrode I a tube 2 is inserted the lower part of which is open, and the upper one closed, but in the cylindrical body of the tube, near the latter part, holes I are provided which are those permitting the circulation of the liquid metal at a speed varyin according to the various temperatures of the tip of the electrode.

Tube 2 is fixed by any proper means, or by welding to the head or sealing plug l of the central electrode I so as to form a perfectly tight closure.

As the sectional area of tube 2 is less than half the sectional area of the internal cavity of the central electrode, the internal liquid consisting of sodium melting at about C. and boiling at about 740C or other fusible metal alloy, circulates continually on the inner surface of the central electrode to thendescend through tube 2, colder towards the tip of the electrode.

A cone 4 of wrought or compressed copper or other good heat conducting metal such as aluminum bronze or silver, externally surrounds fora certain length the central electrode, thereby abstracting, on the whole of the said length, the heat yielded by the liquid metal circulating in the interior of the central electrode. From the cone 4 of copper or other metal the heat is transmitted to collar 5 forming a tight stopper,-and thence passes to the external body or mass electrode 6.

Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed, I declare that what I claim is:

1. A spark plug for explosion and internal combustion engines comprising a hollow central electrode having a closed bottom and a plug for sealing the top, a cooling means completely filling said electrode in the form of metallic sodium having a low melting point and a high ebullition point, a small tube depending from the plug and immersed in the filling and open at the bottom and provided with holes near the sealing plug for facilitating the circulation by gravity of the metallic filling after liquefying along the walls of the hollow electrode.

2. A spark plug for explosion and internal combustion engines comprising an inner central tubular electrode having a closed bottom and an open top, a plug for sealing the top of the electrode,

cooling means within said electrode having a 'low melting point below C. and a high boiling point between 500 C. and 750 C., a metallic tube depending from the plug and immersed in the cooling means in said electrode and spaced from the bottom thereof, said tube being open at the bottom and provided with holes adjacent theupper end near the sealing plug, said tube facilitating the circulation by gravity of the cooling means along the inner wall of said central electrode.

' AURELIO POBBEN'I'I. 

